Radiant ovens generate heat by the use of radiant heaters. In many radiant ovens the radiant heaters are contained in the same oven cavity where the item to be heated is placed. While this is acceptable in many applications, in some cases the item to be heated should not be directly exposed to an electric radiant heater. An example of this is heat-treatment of solvent-laden fabric or web.
In treating web or fabric, it is often necessary to heat the web or fabric to drive off solvent. The solvent vapors can create a fire or explosion hazard, however, if they contact a heating element, especially if failure of the heating element creates a short circuit or other source of ignition. The area of the oven in which solvent vapors accumulate is referred to as the classified area. Spaces that remain free of solvent vapors are referred to as nonclassified areas.
To avoid the fire or explosion hazard caused by solvent vapors, special classified electric radiant heaters are used. Classified electric radiant heaters are designed to be used in classified areas of an oven and reduce or eliminate the possibility of solvent ignition. The drawback to their use is their increased cost.
To reduce expense and improve maintainability, it would be advantageous to be able to use nonclassified electric radiant heaters in or adjacent to the classified area of ae web- or fabric-treating oven. There is a need for a radiant oven utilizing nonclassified electric radiant heaters that can treat items in situations that heretofore required the use of classified electric radiant heaters.